1. Field of the Invention
The invention relates to a process for producing a lubricant base stock from Fischer-Tropsch wax without a dewaxing step. More particularly the invention relates to producing a lubricant base stock from a Fischer-Tropsch synthesized, waxy hydrocarbon fraction, by hydroisomerizing a fraction having an initial boiling point in the range of 650-750.degree. F.+ over a dual function catalyst comprising catalytic metal and acidic oxide components, to convert at least 60 wt. % of the 650-750.degree. F.+ fraction to lower boiling material, and to a fully formulated lubricant comprising an admixture of the base stock and at least one lubricant additive.
2. Background of the Invention
Lubricating oils of low pour point are achieved from petroleum derived feeds such as distillate fractions and slack wax by hydrotreating, solvent extraction and either solvent or catalytic dewaxing. Due to increasing demands on lubricating oil performance and dwindling oil reserves of high quality, the production of synthetic lubricating oils from Fischer-Tropsch synthesized hydrocarbons has received increasing attention, particularly in view of the relatively large amounts of natural gas reserves which need to be converted into more valuable liquid products at the gas well sites and the relatively high purity and highly paraffinic nature of the synthesized hydrocarbons. All of the processes so far suggested for making a lubricant base stock from waxy Fischer-Tropsch synthesized hydrocarbons employ a catalytic or solvent dewaxing step. For example, U.S. Pat. No. 4,963,672 discloses a process comprising hydrotreating, hydroisomerizing and solvent dewaxing Fischer-Tropsch waxy hydrocarbons to produce a high VI and low pour point lube oil base stock. U.S. Pat. No. 5,059,299 discloses hydroisomerizing a Fischer-Tropsch wax and then solvent dewaxing the isomerate to produce a high viscosity index and low pour point lube oil base stock. EP 0 668 342 A1 and EP 0 776 959 A2 disclose hydroconverting a Fischer-Tropsch waxy feed and either catalytically or solvent dewaxing the hydroconvertate. It would be desirable to be able to produce a satisfactory lubricant base stock from Fischer-Tropsch wax without a dewaxing step.